如何在 android 中刷新微调器 onItemSelected 上的片段

Question

我有一个带有微调器和列表视图的片段，当用户从微调器中选择一个选项时，列表视图会更新，我想到我必须在选择一个选项时刷新片段.但问题是当我从“onItemSelected”刷新片段时片段进入无限循环所以我做了一个“refreshFragment 方法”来解决这个问题但是现在在用户选择一个选项后微调器的第一个选项不刷新再次片段，除第一个选项外，所有其他选项都运行良好，因为我没有将“refreshFragment 方法”添加到此选项中，因为如果我添加它，它将再次进入无限循环。

    public class MatchesFragment extends Fragment implements SwipeRefreshLayout.OnRefreshListener, AdapterView.OnItemSelectedListener {
    
        private RecyclerView recyclerView;
        private MatchAdapter matchAdapter;
        private ArrayList<Matches> matchCollection;
        SwipeRefreshLayout mSwipeRefreshLayout;
    
        String apiLink;
        String apiType = "1";
    
    
        public MatchesFragment() {
            // Required empty public constructor
        }
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }
    
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            // Inflate the layout for this fragment
            return inflater.inflate(R.layout.fragment_matches, container, false);
        }
    
        @Override
        public void onActivityCreated(@Nullable Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);
    
            mSwipeRefreshLayout = (SwipeRefreshLayout) getView().findViewById(R.id.swiperefresh);
            mSwipeRefreshLayout.setOnRefreshListener(this);
    
    
            if (getArguments() != null) {
                Bundle arguments = getArguments();
                apiLink = arguments.getString("ApiLink");
                apiType = arguments.getString("apiType");
                Toast.makeText(getContext().getApplicationContext(), apiType, Toast.LENGTH_LONG).show();
            }else {
                apiLink = "http://first-api-link";
                Toast.makeText(getContext().getApplicationContext(), "nothing", Toast.LENGTH_LONG).show();
            }
    
            Spinner spinner = (Spinner) getView().findViewById(R.id.spinner);
            spinner.setOnItemSelectedListener(this);
    
    // Create an ArrayAdapter using the string array and a default spinner layout
            ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(getActivity(),
                    R.array.planets_array, android.R.layout.simple_spinner_item);
    // Specify the layout to use when the list of choices appears
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    // Apply the adapter to the spinner
            spinner.setAdapter(adapter);
    
            ConnectivityManager cm = (ConnectivityManager) getContext().getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);
    
            NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
            String answer = "Internet";
            if (null != activeNetwork) {
                if(activeNetwork.getType() == ConnectivityManager.TYPE_WIFI)
                    answer="You are connected to a WiFi Network";
                if(activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE)
                    answer="You are connected to a Mobile Network";
                init();
                new FetchDataTask().execute();
            }
            else {
                answer = "No internet Connectivity";
                Toast.makeText(getContext().getApplicationContext(), answer, Toast.LENGTH_LONG).show();
            }
        }
    
        private void init() {
            recyclerView = (RecyclerView) getActivity().findViewById(R.id.matchesRecyclerview);
            recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
            recyclerView.setHasFixedSize(true);
            matchCollection = new ArrayList<>();
            matchAdapter = new MatchAdapter(matchCollection, getActivity());
            recyclerView.setAdapter(matchAdapter);
        }
    
        @Override
        public void onRefresh() {
            init();
            new FetchDataTask().execute();
        }
    
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    
            apiLink = "http://first-api-link";
            switch (position){
//can't add refreshFragment in here it makes infinity lopp
                case 0: apiLink = "first-api-link";
                break;
                case 1:
                    refreshFragment("second-api-link", 2);
                break;
                case 2:
                    refreshFragment("third-api-link", 3);
                    break;
                case 3:
                    refreshFragment("fourth-api-link", 4);
                    break;
                case 4:
                    refreshFragment("fifth-api-link", 5);
                    break;
                case 5:
                    refreshFragment("sixth-api-link", 6);
                    break;
            }
        }
    
        @Override
        public void onNothingSelected(AdapterView<?> parent) {
    
        }
    
        public class FetchDataTask extends AsyncTask<Void, Void, Void> {
            private String mZomatoString;
    
            @Override
            protected Void doInBackground(Void... params) {
                HttpURLConnection urlConnection = null;
                BufferedReader reader = null;
                Uri builtUri = Uri.parse(apiLink);
                URL url;
                try {
                    url = new URL(builtUri.toString());
                    urlConnection = (HttpURLConnection) url.openConnection();
                    urlConnection.setRequestMethod("GET");
                    urlConnection.setRequestProperty("user-key", "acfd3e623c5f01289bd87aaaff1926c1");
                    urlConnection.connect();
    
                    InputStream inputStream = urlConnection.getInputStream();
                    StringBuffer buffer = new StringBuffer();
                    if (inputStream == null) {
                        //Nothing to do
                        return null;
                    }
    
                    reader = new BufferedReader(new InputStreamReader(inputStream));
    
                    String line;
                    while ((line = reader.readLine()) != null) {
                        buffer.append(line + "\n");
                    }
    
                    if (buffer.length() == 0) {
                        return null;
                    }
    
                    mZomatoString = buffer.toString();
                    JSONObject jsonObject = new JSONObject(mZomatoString);
    
                    Log.v("Response", jsonObject.toString());
    
                    JSONArray matchArray = jsonObject.getJSONArray("data");
    
    
                    //list = new ArrayList<>();
                    for (int i = 0; i < matchArray.length(); i++) {
    
                        Log.v("BRAD_", i + "");
                        String home_team;
                        String away_team;
                        String home_flag;
                        String away_flag;
    
                        JSONObject jTeam = (JSONObject) matchArray.get(i);
    
                        if (apiType == "1"){
                        JSONObject jHomeTeam = (JSONObject) jTeam.getJSONObject("home_team");
                        JSONObject jAwayTeam = (JSONObject) jTeam.getJSONObject("away_team");
    
                        //get data's from json sent from link
                        home_team = jHomeTeam.getString("name");
                        away_team = jAwayTeam.getString("name");
                        home_flag = jHomeTeam.getString("flag");
                        away_flag = jAwayTeam.getString("flag");
                        }else{
                            //get data's from json sent from link
                            home_team = jTeam.getString("home_team");
                            away_team = jTeam.getString("away_team");
                            home_flag = "https://www.countries-ofthe-world.com/flags-normal/flag-of-Russia.png";
                            away_flag = "https://www.countries-ofthe-world.com/flags-normal/flag-of-Russia.png";
                        }
    
    
    
                        Matches matches = new Matches();
                        matches.setHome_team(home_team);
                        matches.setAway_team(away_team);
                        matches.setHome_flag(home_flag);
                        matches.setAway_flag(away_flag);
    
                        matchCollection.add(matches);
                        // Stopping swipe refresh
                        mSwipeRefreshLayout.setRefreshing(false);
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (JSONException e) {
                    e.printStackTrace();
                } finally {
                    if (urlConnection != null) {
                        urlConnection.disconnect();
                    }
                    if (reader != null) {
                        try {
                            reader.close();
                        } catch (final IOException e) {
                            Log.e("MainActivity", "Error closing stream", e);
                        }
                    }
                }
                return null;
            }
    
            @Override
            protected void onPostExecute(Void aVoid) {
                matchAdapter.notifyDataSetChanged();
            }
        }
    
        public void refreshFragment(String apiLinks, int apiType){
            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            MatchesFragment fragment = new MatchesFragment();
            Bundle args = new Bundle();
            args.putString("ApiLink", apiLinks);
            args.putString("apiType", String.valueOf(apiType));
            fragment.setArguments(args);
            fragmentTransaction.replace(R.id.linearfr, fragment);
            fragmentTransaction.commit();
        }
    
    }

Answer 1

使用微调器时需要考虑一些事项。它总是有一个 selected 值，默认值 selected 是第一个。因此，当创建片段时，微调器中的第一个值是 selected.

当您第一次手动打开下拉列表和 select 第一项时，目前默认为 selected，因此您的 selection 不会被触发，因此不调用刷新。诀窍是将虚拟项目添加为第一个项目并忽略 onItemSelected 中的位置 0（您已经在这样做）。

发生无限循环是因为在创建视图时默认情况下微调器 select 是第一项，因此触发位置 0 的 onItemSelected 再次调用刷新、更改片段、新微调器已创建，第一项已 selected，恶性循环继续。

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